It is the current practice in packaging insulated communication wire or cable in a carton to coil the wire in a FIG. 8 configuration of the coil which is used to reduce twisting of the wire as it is coiled, thereby reducing a tendency of the wire to kink as it is pulled from the carton, generally through an opening in a side wall thereof. The pulling process is facilitated by the installation of a pay-out tube which extends into the interior of the carton, and which is affixed to a wall thereof in a suitable manner so as, generally, to have a stub portion extending outside of the carton. In U.S. Pat. No. 5,152,476 of Moser, there is shown a preferred arrangement for affixing the tube to the wall of the carton having a modified bayonet lock type of action. Numerous prior art arrangements utilize this arrangement, or modifications thereof, for mounting the tube. Generally, such arrangements require that the tube be mounted from inside the carton and twisted to engage the bayonet lock. This operation is difficult to perform by hand, especially when the carton is full, as it usually is, since the pay-out tube generally cannot be installed until after the cable is placed in the carton.
Most tubes in use today are in the form of hollow elongated cylinders with the ends thereof being radiused between the outer and inner walls to eliminate sharp corners over which the wire passes as it is pulled through the tube. Such radiused ends are shown in U.S. Pat. Nos. 5,064,136 and 5,115,995 of Hunt. In these arrangements, the entrance end surface substantially conforms to a hemi-toroidal surface having a faired joinder at its inner and outer margins with the inner and outer walls of the tube. Such a rounded surface imposes a lower limit on the bend radius of the wire being pulled through the tube, which however, does not prevent kinking of the wire or damage to its insulation when the wire is being pulled from layers immediately adjacent to the tube and lying between the end of the tube and the wall in which the tube is mounted. In that case, the wire undergoes a sharp reverse bend as it enters the tube, and the radiused end of the tube is insufficient to prevent kinking and possible damage.
The aforementioned Moser patent discloses an end cap for the entrance end of the pay-out tube which greatly increases the minimum possible radius of curvature of the wire, thereby materially reducing the tendency of the wire to kink even in the extreme reverse bend case discussed in the foregoing.
However, any cap arrangement for the pay-out tube gives rise to the additional problem of the introduction of a separate part, with the possibility of its being lost or mislaid. Also, the fabrication of such a separate part requires additional molds and fabrication steps, thereby increasing the cost of the pay-out tube assembly. Moser apparently recognizes the problem at least to some extent, by suggesting that the cap and the pay-out tube may be fused together to produce a single unitary structure, but apparently the two parts are intended to be fabricated separately and then joined, with a consequent two molding operations, hence, an increase in production costs.
In U.S. Pat. No. 5,520,347 of Bass et al. there is disclosed a one-piece pay-out tube which overcomes the aforementioned disadvantages of the Moser device as well as many other prior art devices. The Bass et al (hereinafter "Bass") pay-out tube has a flange at the cable entrance end thereof which has a radiused surface, the radius being greater than the kinking radius R.sub.c, and a central opening where the radiused surface fairs into the inner wall of the tube, with the inner wall being tangential to the radiused surface. The opposite or cable exit end of the tube has a mounting arrangement which is strengthened by suitable ribs and strength members, which are cast or formed integral with the remainder of the tube. The Bass patent is incorporated herein by reference.
In use, a pay-out tube functions to guide wire or cable out of the carton in, preferably, an unkinked condition, with a reasonable ease of pay-out. However, it is seldom the case that all of the wire contained in a carton is payed out at one time, i.e., in a single operation, and usually, after the desired length of cable has been pulled out, the cable is cut. When this occurs, the cable, which has been under tension, tends to spring back into the carton where it becomes inaccessible in the extreme case. Numerous arrangements have been used to prevent the cable from thus springing back, and for holding it fixed within the tube. One arrangement common in the prior art and shown in the Bass patent is a resilient diaphragm formed of wedge-shaped fingers adjacent the cable entrance end of the tube. The fingers are resilient enough to yield to the cable as it is pulled out under tension, but sufficiently stiff enough to resist the tendency for the cable to spring back after being cut, thereby holding the cable in place provided the spring back action is not to strong. U.S. Pat. Nos. 5,152,476 of Moser, 5,064,136 of Hunt and 4,274,607 of Priest all show such diaphragm arrangements. Provided wire or cable tension is not excessive, such diaphragms perform adequately, but, as is the usual case, being integrally formed with the tube, they require complex mold designs which materially increase costs. In the aforementioned pending Bass et al. patent application, the diaphragm arrangement is dispensed with in favor of tapered compartments on the inner walls of the tube which receive the end of the cable and prevent it from springing back into the carton. In addition to being a single molded member, and, hence, economical to manufacture, this arrangement is especially effective with stiff cables, more so than the diaphragm arrangement.
In virtually all of the foregoing prior art pay-out tubes, some form of bayonet lock or latch is used to anchor the tube in place in the carton. As pointed out hereinbefore, mounting such a tube within the carton requires inserting the tube into an exit hole in the carton from within the carton, and then twisting the tube to lock it in place.
What is needed, therefore is a pay-out tube of, preferably, one piece molded construction, that does not require any twisting action to lock it in place, being mountable to the carton with a simple axial movement.